Norethisterone (or norethindrone) (or 19-nor-17α-ethynyltestosterone) is a molecule used in some combined oral contraceptive pills and in some progestogen only pills. It is a progestogen and can be used to treat premenstrual syndrome, painful periods, abnormal heavy bleeding, irregular periods, menopausal syndrome (in combination with oestrogen), or to postpone a period. Norethindrone was the first orally highly active progestin to be synthesized. It was synthesized for the first time by chemists Luis Miramontes, Carl Djerassi, and George Rosenkranz at Syntex in Mexico City in 1951. It was the progestin used in one of the first two oral contraceptives. It is often used as the related ester, norethisterone acetate.